1. Field of the Invention
The present invention relates to a method of precharging a word line of a semiconductor memory device, and more particularly to, a method of precharging a word line capable of achieving a page mode embodiment and a speed improvement in a pseudo SRAM.
2. Discussion of Related Art
A semiconductor memory device is used in many kinds of applicable fields. As a result, according to each case, a definition to operation of a semiconductor memory device is differentiated to adapt for usage of each applicable field. For instance, a pseudo SRAM requires a less power consumption and a low operation frequency, relatively, comparing with the conventional SRAM in case of a main application circumstance.
As it is, during a read operation of the pseudo SRAM, when a corresponding word line is accessed and a sensing operation is completed by a sense amplifier, a precharge signal is generated. The corresponding word line is enabled according to the precharge signal and then an operation is performed to take an address for a new word line access operation from an address buffer. However, in order to operate a page read mode, a word line should have been enabled but the conventional technique takes the address from the address buffer only after precharging, so that it is disadvantageous to reduce a read speed.
It will be described about the conventional art with reference to FIGS. 1 and 2 in detail.
When a word line enable active condition is satisfied, an active command generation unit 60 generates a word line active signal wl_active.
The word line enable active condition is one of those as follows that 1) when a chip select signal CS1 is transited from high level to low level, 2) when an address is toggled, 3) when a write enable signal /WE is transited from low level to high level, 4) when a select signal of an upper memory block and/or a lower memory block UB and/or LB is transited from high level to low level, 5) when the write enable signal /WE is transited from high level to low level for the first time after a power up, 6) when a page address is toggled for the first time after the power up, and 7) after a refresh operation.
The word line active conditions are satisfied, an address strobe signal Address strobe is generated and then receives an address information entering into an address buffer 10. The address entered from the address buffer 10 is pre-decoded in a pre-decoder 20 and then is decoded by a decoder 30. Also, the word line active signal wl_active delayed in a delay unit 40 is enabled and thus a word line W/L is accessed.
After the active condition is satisfied and then another operation, that is, a refresh or the aforementioned active condition is entered, if a new active condition is satisfied, the word line enable signal wl_active is generated and then the address strobe signal Address strobe isn't immediately generated. After a precharge signal PCG is generated, the word line W/L access operation is achieved by completing pre-decoding and decoding operations and enabling the word line enable signal wl_active by means of receiving a new address according to the address strobe signal Address strobe.
Referring to FIG. 2, as soon as a sense delay signal sensedly is generated after a sensing operation during a read operation, the precharge signal PCG is generated in a precharge signal generation unit 50. The precharge signal PCG disables the previous word line. In this case, although the new active condition is satisfied, the precharge signal PCG has disabled the word line (that is, a page is closed), by which cause the page read operation not to be performed. Additionally, it is disadvantageous that a speed is not fast because the operation taking the address is possibly performed after the precharge operation.